Overview

Nimio is a lightweight, flexible JavaScript player for the SLDP 2.0 protocol built on the WebCodecs API. It offers low-latency streaming, full control over audio/video pipelines, and easy integration into modern web apps.

Demo

https://nimio.pages.dev/demo - Latest

https://softvelum.com/nimio/demo/ - Stable

Player highlights

• Ultra-low latency SLDP 2.0 over WebSockets with WebCodecs; supports H.264/H.265/AV1/VP8/VP9 plus AAC/MP3/Opus.
• Adaptive streaming
• Integrated player UI
• Latency and sync control: target + tolerance, fast-forward/seek correction, audio gap smoothing, timestamp recovery.
• Audio-only/video-only modes
• Full screen playback
• VU meter
• EventBus hooks for custom UI/analytics

SLDP & WebCodecs Features

• SLDP Protocol (Softvelum Low Delay Protocol) - WebSocket‑based streaming with sub-100ms latency, supporting H.264, H.265/HEVC, AV1, VP8, VP9, AAC, MP3, Opus, and more.
• WebCodecs Integration - Fine‑grained control over decoding, synchronization, jitter buffering, playback speed, and debugging at each stage of the pipeline.
• Available on all web platforms - desktop, Android and recent iOS/macOS.

Read the first beta release announcement with the list of current features.

Quick Start

<script type="module" src="/dist/nimio.js"></script>

<div id="player"></div>

<script>
  const nimio = new Nimio({
    streamUrl: "wss://example.com/stream",
    container: "#player",
  });
</script>

Full Configuration Example

nimio = new Nimio({
  streamUrl: "wss://example.com/stream", //SLDP stream URL
  container: "#player", // CSS selector or HTMLElement
  //optional parameters:
  width: 476,
  height: 268,
  latency: 600, // Target latency in ms
  startOffset: 1000, // Startup offset in ms
  pauseTimeout: 3000, // ms until auto-stop when paused
  metricsOverlay: true, // Show overlay with performance metrics
  logLevel: "warn", // Logging verbosity
  autoplay: true, // Start playback automatically
  videoOnly: false, // Video only playback
  audioOnly: false, // Audio only playback
  muted: true, // Player is muted on start
  hardwareAcceleration: false, // Request hardware decoder; falls back to software if unsupported
  adaptiveBitrate: {
    initialRendition: "480p", // Default rendition which the player will set on start
    maxRendition: "1080p", // Maximum rendition that the player will set automatically
    sizeConstrained: true, // Player won't automatically switch to renditions which dimensions exceed the actual player size more then 5%
  },
  vuMeter: {
    // a volume unit (VU) meter settings object
    api: "AudioWorklet", // audio processing interface used by VU meter ("AudioWorklet" or "ScriptProcessor")
    container: "vu-meter", // ID of the VU meter container. VU meter UI  occupies the whole container's size. Vertical orientation (container's height >= width), horizontal orientation (container's width > height)
    mode: "peak", // the way which audio level values are calculated ("peak", "avg", "rms")
    type: "input", // VU meter readings type ("input" or "output")
    rate: 6, // audio level update frequency limit (from 0.001 to 50)
    dbRange: 100, // decibel scale range which is plotted in the VU meter UI
  },
});

nimio.play();

Multiple players

Mosaic demo (multiple players on one page): docs/mosaic-demo.md

Cross‑Origin Isolation

Nimio tries to use SharedArrayBuffer for zero‑copy state/audio exchange, but now falls back to a message‑based path when it is unavailable.
For best latency you should still enable a fully isolated browsing context by sending both the Cross‑Origin‑Opener‑Policy and Cross‑Origin‑Embedder‑Policy headers on any page or asset that loads the player.

Add these two headers:

add_header Cross-Origin-Opener-Policy  same-origin always;
add_header Cross-Origin-Embedder-Policy require-corp always;

Example: Nginx Configuration

server {
    listen 443 ssl;
    server_name example.com;

    # Serve the Nimio demo with COOP/COEP
    location ^~ /nimio/ {
        alias /usr/share/nginx/example.com/nimio/;
        index index.html;

        # Enable cross‑origin isolation
        add_header Cross-Origin-Opener-Policy  same-origin always;
        add_header Cross-Origin-Embedder-Policy require-corp always;
    }
}

Methods

Instance Methods

These methods are available on every Nimio player instance.

• play()
  Start playback.
• pause()
  Pause playback.
• stop()
  Stop and reset the player.
• version()
  Return the current version string of this player instance.

Static Methods

These methods are available directly on the Nimio class.

• Nimio.version()
  Return the current version string (identical to instance.version()).

Events

Nimio player uses events to interact with its UI. It allows to create custom UI easily.

Events sent from UI to player

These events are used to send commands and data from UI to Nimio player.

• ui:play-pause-click
  Start/pause playback.
  Parameters:

isPlayClicked: Boolean;

• ui:mute-unmute-click
  Mute/unmute audio.
  Parameters:

mute: Boolean;

• ui:volume-change
  Set audio volume.
  Parameters:

volume: Number; // Current volume as integer value in the range from 0 to 100.

• ui:rendition-change
  Change ABR rendition. Should be form the list received with nimio:rendition-list event.
  Parameters:

   rendition: {
     id: Number, // An integer number with unique rendition ID.
     name: String // Rendition name.
   }

Events sent from player to UI

These events are used to send data from Nimio player to UI.

• nimio:play
  Playback started.
  Parameters:

instanceName: String; // Player instance name
containerId: String; // Container ID, where player is rendered

• nimio:muted
  Audio muted/unmuted.
  Parameters:

muted: Boolean;

• nimio:volume-set
  Audio volume set.
  Parameters:

volume: Number; // Current volume integer value in the range from 0 to 100.

• nimio:abr
  Adaptive bitrate enabled/disabled.
  Parameters:

isAbr: Boolean;

• nimio:rendition-set
  ABR rendition set.
  Parameters:

   rendition: {
     id: Number, // An integer number with unique rendition ID.
     name: String // Rendition name.
   }

• nimio:rendition-list
  An array of ABR renditions available.
  Parameters:

  renditions: [
   {
     id: Number, // An integer number with unique rendition ID.
     name: String // Rendition name.
   },
   ...
 ]

Roadmap

The following features are planned for upcoming releases:

• Automatic aspect ratio detection
• Picture-in-Picture (PiP)
• Latency retention for asynchronous renditions
• CEA-608 closed captions
• VOD playback (DVR support)
• VOD thumbnail previews
• SEI timecodes support
• WebTransport protocol
• Nimble Advertizer integration
• Automatic reconnection
• Sync mode
• Screenshot capture
• Splash/startup image
• Extended Player API
• Muted autoplay
• Dynamic latency adjustment
• OffscreenCanvas rendering
• Resume from pause in DVR mode (no auto-jump to live)

Contributing

Contributions are welcome! Please open an issue for discussion or submit a pull request.

License

Nimio released under MIT License.